Local protein synthesis within dendritic spines has long been hypothesized to provide a synapse specific mechanism for the control of spine development and synaptic plasticity. An inherent difficulty in testing this hypothesis has been the lack of suitable methods to directly visualize and quantify local translation with sufficient spatil and temporal resolution. While numerous mRNAs have been localized to dendrites by in situ hybridization methods, only a few have been directly shown to be locally translated in dendrites using fluorescent reporters, and technical limitations often preclude visualization of the precise loci where translation occurs and how translational responses are regulated by physiological signals within a morphologic context. Thus, a critical gap is lack of suitable methods to address fundamental questions about the types of mRNAs that are translated in spines, and to ask questions about the underlying regulatory mechanisms and their function in protein sorting and spine development. Related to this major gap in knowledge, a fundamental but as yet unanswered question is whether membrane proteins can be translated in or near spines, and whether mechanisms exist to couple synthesis with trafficking to the cell surface in response to plasticity inducing stimuli. Our goal for the proposed research is to develop and apply a single molecule imaging approach using fluorescent reporters in microfluidic devices to visualize and quantify translational events within dendrites and spines. Aim 1 will investigate the hypothesis that local translation of receptors and channels occurs locally in spines and that mechanisms of synthesis and surface expression are coordinately regulated by plasticity inducing stimuli. Aim 2 will investigate the hypothesis that dendritic microRNAs are necessary for both the activity regulated local translation and surface expression of membrane proteins in response to plasticity inducing stimuli. We anticipate that development and application of this technological approach will uncover novel mechanisms for receptor-mediated regulation of local mRNA translation in dendritic spines that play important roles in protein trafficking and neuronal development. We anticipate that the proposed research will lead to a new perspective on how local translation is under spatiotemporal control by synaptic mechanisms that are likely impaired in neurologic disorders, including epilepsy, fragile x syndrome and schizophrenia.